The present invention relates to devices and techniques for measuring arsenic concentrations, and more specifically for quantitative measurements of arsenic concentrations in aqueous solutions. The invention may be used for field measurements of arsenic concentrations in groundwater.
International Patent Application No. PCT/US03/026484, incorporated by reference herein, describes a portable arsenic meter for testing and measuring the arsenic concentrations in samples of ground water. The portable arsenic meter exploits differential infrared measurements of arsenic color complexes formed in test water samples. The test water samples are pre-treated with oxidizing and reducing agents to alter the oxidation state of arsenic to arsenate and arsenite states, respectively. Different color complexes are formed in the test water samples by adding a color reagent (e.g., an ammonium molybdate based acid reagent) that selectively incorporates arsenic according to its oxidation sate, arsenate As (V) or arsenite As (III).
The portable arsenic meter is designed for use in adverse field conditions. The portable arsenic meter may be included a test kit, which can be operated in third world conditions, for example, by people with little or no specialized training, to measure extremely low concentrations of arsenic.
Consideration is now being given to further simplify the use of the portable arsenic meter in the field. In particular, attention is paid to the preparation chemistries utilized to make the arsenic color complexes and the form of chemical reagents used.